Wear-protection coatings, in particular in the form of coatings of hard material based on a carbonitride, are known in single-layer or multiple-layer structure with layer thicknesses in the micron range, both on tools and on parts.
Disadvantages of such coatings are the often relatively high coefficients of friction, occurrence of intrinsic tensions and resulting reduction of adhesive strength, and the great brittleness in comparison to the hardness. Furthermore, improving the wear-resistance of these coatings by increasing the hardness has a detrimental effect on other desired properties, such as toughness, impact resistance and substrate adhesion.
In addition to hard material coatings based on a carbonitride, friction-reducing wear-resistant coatings of diamond-like carbon (DLC) and molybdenum disilicide are also known. However, their disadvantages include their relatively low abrasion resistance, inadequate resistance to media, and limited temperature resistance, less than 350° C. in the case of DLC.
To overcome the named disadvantages, functional coatings that are already nanostructured have also been developed, in which a nanocrystalline phase is present that is embedded in an amorphous or crystalline matrix phase.
The primary methods used to produce such nanostructured coatings are CVD (chemical vapor deposition) and PVD (physical vapor deposition). In particular, the PVD methods, such as magnetron sputtering or arc vaporization, are characterized by great flexibility in the selection of material, and hence offer the possibility of influencing or adjusting the layer structure in a controlled manner according to the desired application.
It is proposed for example by R. Hauert et al., Advanced Materials, 11, No. 2 (1999), pp. 175-177, that a PACVD process (plasma activated chemical vapor deposition) be used to embed nano-scale titanium nitride particles having a particulate size of 10 nm to 20 nm in an amorphous silicon nitride matrix or a matrix of amorphous silicon.
M. Diserens et al., Interface and Coatings Technology, 108 to 109 (1998), pp. 241-246, describe a PACVD method in which a nanostructured (TI, Si)N coating is produced on a substrate in a vacuum chamber at temperatures under 350° C. using a magnetron sputtering method (reactive unbalanced magnetron sputtering). Specifically, nano-scale or nanocrystalline titanium nitride particles having a mean crystallite size of around 20 nm are present there, embedded in an amorphous silicon or silicon nitride matrix. To ensure an additional input of power during deposition of the coating on the substrate, a high-frequency substrate voltage (bias voltage) between 0 V and −140 V is also applied there to the substrate being coated.
Finally, German Published Patent Application No. 101 04 611 contains a description of a device for coating a substrate with a ceramic-like coating, whereby a material is deposited on a substrate using a source of material and a plasma. There, a power source that is different from the source of material is provided to input power at a defined location into the material which is in front of or on the surface.